The Facebook Effect: Foursquare Had Its Most Signups Ever Today — Leading up to Facebook's location announcement, there were two schools of thought. Either you thought Facebook Places was going to destroy Foursquare. Or you thought that this new service would help the startup by bringing more awareness to the location field.

The Confusing Stages Of Opting Into Facebook Places — Earlier today we had a bit of a fire-drill at TechCrunch Headquarters. As I checked into TCHQ on Facebook Places, I also tagged a few of my coworkers, fully expecting their checkins to be delayed until they actually opted into the feature …

To 100 million and beyond with Google Maps for mobile — Almost five years ago, we launched Google Maps for mobile to help you get where you needed to go from your phone instead of a paper map. Today, more than 100 million people a month are now using Google Maps for mobile to get from point A to point B …

Google's social czar picks a location fight with Facebook — Google's timing can be peculiar — but rarely coincidental. A day after Facebook launched its first location feature, the search giant revealed in a blog post Thursday that more than 100 million users check Google Maps on mobile devices.

Time Inc. breaks the iPad logjam — This week's People app is free to subscribers. Time, SI and Fortune are expected to follow — Image: Time Inc. — There's more to the iPad issue of People that appeared on the Apple (AAPL) App Store this morning than Sandra Bullock's new joy.

Exclusive: Dell Thunder prototype preview (video) — Christmas came early at Engadget HQ this year, as evidenced by the picture above — you're looking at two Dell Thunder prototype smartphones, each with some surprising quirks, and hints that they might include global HSPA, AWS for T-Mobile, and maybe even a dash of CDMA support.

State of the Art: OpenDNS Simplifies Life for Web Users — I'm about to make your life better. No need to thank me. — But first, a warning: On the way to understanding how your life will get better, you'll have to read about some technical, fairly arcane topics. Trust me: It'll be worth it.

A smartphone retrospective — This is what high-end smartphones looked like in 2007: — Smartphones were an established consumer-electronics market with devices that people thought were pretty cool, but often frustrating and with serious shortcomings and design flaws. — Then this happened:

HP: WebOS tablet coming early next year — Hewlett-Packard will release a tablet PC based on Palm's webOS operating system in “early 2011,” the head of HP's PC division said Thursday. — Hewlett-Packard will release a tablet PC based on Palm's webOS operating system in “early 2011,” the head of HP's PC division said Thursday.

Apple adds “Compare Macs” option to Apple Store — Apple on Thursday added a new option to its online Apple Store called “Compare Macs.” — The new option allows customers to quickly bring up specs on the hardware, included software and technical specifications for each system.

When Attorneys General Attack — Earlier this year Topix CEO Chris Tolles got the call no one wants to get - that they are under investigation by a government entity. Two attorneys general, one of which was deep into his senate run, were leveling accusations of abuse at Topix.

Google voice and video - now available for Linux! — Google voice and video chat is now available in Gmail for Ubuntu and other Debian-based Linux distributions. As the comments on this blog indicate, I know many folks have been waiting very patiently for this day!

Rogue Apple Exec Trashes Rivals' ‘Mediocre Engineers’ — It's amazing that Phillip Shoemaker still works at Apple. The app store director obsessed with porn and escorts, as we reported yesterday, has also used Twitter to attack execs at rival companies and media critics, we've learned.

Groupon Having A $4 Million Day Thanks To The Gap — Groupon is having a smashing day, likely generating over $4 million in net revenue, thanks to a deal with the Gap. — Today's Groupon gives users a $25 discount at the Gap if consumers spend over $50 at the store.